The exemplary embodiments described herein relate to methods of manufacturing a semiconductor device having superior reliability.
As the electronics industry has developed, mobile communication devices and computers having improved performance are required. To meet these requirements, a semiconductor device having a high operational speed (for example, during read/write operations), a nonvolatile characteristic and a low operational voltage is required.
A unit cell of a widely used DRAM includes one capacitor and one transistor controlling the capacitor. Thus, a DRAM needs relatively a large unit cell area compared with that of a NAND flash of a string structure. Also, a DRAM is a volatile memory device, losing its stored data when a power supply is interrupted. In contrast, a flash memory is a nonvolatile memory device, maintaining stored data when a power supply is interrupted. However, since an operation of a flash memory is based on a tunneling phenomenon, operational speed is slow.
Accordingly, a study of a phase change memory device as a next generation memory having a high operational speed and a nonvolatile characteristic has been increased in importance. A unit cell of the phase change memory device is an element storing data and may include a phase change material. The phase change material may have states having different resistances. For example, a phase change material of a crystalline state may have a resistance lower than a phase change material of an amorphous state. A crystalline state of a phase change material can be controlled through a condition of a melting process and a cooling process.
Development of a manufacturing process of a phase change memory device is required with reference to a material problem and a structural problem of a phase change memory device.